Created
March 29, 2019 11:19
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API Client with pure URLSession
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| enum HTTPMethod: String { | |
| case get = "GET" | |
| case put = "PUT" | |
| case post = "POST" | |
| case delete = "DELETE" | |
| case head = "HEAD" | |
| case options = "OPTIONS" | |
| case trace = "TRACE" | |
| case connect = "CONNECT" | |
| } | |
| struct HTTPHeader { | |
| let field: String | |
| let value: String | |
| } | |
| class APIRequest { | |
| let method: HTTPMethod | |
| let path: String | |
| var queryItems: [URLQueryItem]? | |
| var headers: [HTTPHeader]? | |
| var body: Data? | |
| init(method: HTTPMethod, path: String) { | |
| self.method = method | |
| self.path = path | |
| } | |
| init<Body: Encodable>(method: HTTPMethod, path: String, body: Body) throws { | |
| self.method = method | |
| self.path = path | |
| self.body = try JSONEncoder().encode(body) | |
| } | |
| } | |
| struct APIResponse<Body> { | |
| let statusCode: Int | |
| let body: Body | |
| } | |
| extension APIResponse where Body == Data? { | |
| func decode<BodyType: Decodable>(to type: BodyType.Type) throws -> APIResponse<BodyType> { | |
| guard let data = body else { | |
| throw APIError.decodingFailure | |
| } | |
| let decodedJSON = try JSONDecoder().decode(BodyType.self, from: data) | |
| return APIResponse<BodyType>(statusCode: self.statusCode, | |
| body: decodedJSON) | |
| } | |
| } | |
| enum APIError: Error { | |
| case invalidURL | |
| case requestFailed | |
| case decodingFailure | |
| } | |
| enum APIResult<Body> { | |
| case success(APIResponse<Body>) | |
| case failure(APIError) | |
| } | |
| struct APIClient { | |
| typealias APIClientCompletion = (APIResult<Data?>) -> Void | |
| private let session = URLSession.shared | |
| private let baseURL = URL(string: "https://jsonplaceholder.typicode.com")! | |
| func perform(_ request: APIRequest, _ completion: @escaping APIClientCompletion) { | |
| var urlComponents = URLComponents() | |
| urlComponents.scheme = baseURL.scheme | |
| urlComponents.host = baseURL.host | |
| urlComponents.path = baseURL.path | |
| urlComponents.queryItems = request.queryItems | |
| guard let url = urlComponents.url?.appendingPathComponent(request.path) else { | |
| completion(.failure(.invalidURL)); return | |
| } | |
| var urlRequest = URLRequest(url: url) | |
| urlRequest.httpMethod = request.method.rawValue | |
| urlRequest.httpBody = request.body | |
| request.headers?.forEach { urlRequest.addValue($0.value, forHTTPHeaderField: $0.field) } | |
| let task = session.dataTask(with: url) { (data, response, error) in | |
| guard let httpResponse = response as? HTTPURLResponse else { | |
| completion(.failure(.requestFailed)); return | |
| } | |
| completion(.success(APIResponse<Data?>(statusCode: httpResponse.statusCode, body: data))) | |
| } | |
| task.resume() | |
| } | |
| } | |
| /// MARK: - Usage - | |
| struct Post: Decodable { | |
| let userId: Int | |
| let id: Int | |
| let title: String | |
| let body: String | |
| } | |
| let request = APIRequest(method: .get, path: "posts") | |
| APIClient().perform(request) { (result) in | |
| switch result { | |
| case .success(let response): | |
| if let response = try? response.decode(to: [Post].self) { | |
| let posts = response.body | |
| print("Received posts: \(posts.first?.title ?? "")") | |
| } else { | |
| print("Failed to decode response") | |
| } | |
| case .failure: | |
| print("Error perform network request") | |
| } | |
| } |
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